PRRT2 and pancreatic insulinoma: Moreover, the phosphorylation of SNAP-25 at Ser187 by PKC was necessary for the enhancement of Ca2+-triggered exocytosis by phorbol ester in an insulinoma cell line [47], and the inhibition of SNAP-25 phosphorylation at Ser187 down-regulated morphine-induced SNARE complex formation in neurons [48].